In this study, for the first time, a simple immunosensor for ultrasensitive recognition of human chorionic gonadotropin (HCG) in serum samples was fabricated using a simple approach. In this method, a low-cost, sensitive immunosensor was made based on QDs-N-S/Au nanoparticles (NPs) modified screen-printed carbon electrode (SPCE). It seems that QDs-N-S/AuNPs/ antibody as a biocomposite can be a good choice for development as an impressive immunosensor. In modifying the proposed immunosensor, the length of the process was reduced and the use of other substrates was eliminated. The pH and incubation time were optimized as two important parameters. Under the optimal conditions at modified SPCE, a linear communication in the range of 0.1 to 125 pg mL−1 and the detection limit of 12.5 fg mL−1 were obtained. The present procedure was utilized to the detection of HCG in real samples with the desirable results
